Bacillus subtilis and many other bacteria can be transformed by exogenous DNA when in a physiological state known as competence. Competent cells can bind DNA, fragment it on the cell surface and transport a single strand of DNA across the membrane. Once internalized, the single strand can integrate at a homologous site on the recipient chromosome. Our long-term objective is to understand these processes on the molecular level, by characterizing the 20 proteins involved and their interactions with one another and with DNA. We have shown that transformation takes place mostly at the cell poles. This proposal explores the interactions among many of the competence proteins, as well as their localization and delocalization as polar complexes. The recently discovered role of McsA and McsB in delocalization will be explored. We will also detect contacts between these proteins and DNA at various stages in the transformation process and determine the cellular addresses at which the contacts occur. The structure, composition and role of the competence pseudopilus will be explored. The sources of energy driving the transport of transforming DNA will be identified. Genetic screens will be used to find two competence proteins that have not been identified;the nuclease that degrades the non-transforming strand, and a second cell surface DNA binding protein. Transformation provides a mechanism for the horizontal transfer of antibiotic resistance and virulence genes among pathogens. Understanding the mechanism of gene transfer by transformation will provide insights into these important processes. Many bacteria can accept DNA from the environment in a process known as transformation. This provides a mechanism for the horizontal transfer of antibiotic resistance and virulence genes among pathogens. Understanding this process of gene transfer by transformation will provide insights into these important processes.